1. Field of the Invention
The present invention relates to a micromechanical inertial sensor, including at least one ASIC (application specific integrated circuit) element having a processed front side, an MEMS (microelectromechanical systems) element having a micromechanical sensor structure, which includes at least one seismic mass and extends over the entire thickness of the MEMS substrate, and including a cap wafer, which is mounted above the micromechanical sensor structure of the MEMS element. The MEMS element is mounted on the processed front side of the ASIC element above a standoff structure and electrically connected to the ASIC element via through-contacts in the MEMS substrate and in adjacent supports of the standoff structure. In addition, the present invention relates to a method for manufacturing such a micromechanical inertial sensor.
2. Description of the Related Art
Micromechanical inertial sensors are used to detect translatory and rotatory accelerations. They have been manufactured in mass production for many years for a wide range of applications, for example, in the fields of automotive engineering and consumer electronics, where miniaturization of the sensor components has become increasingly important. On the one hand, miniaturization makes a significant contribution toward lowering the manufacturing costs of the sensor components and thus also of the terminal equipment. On the other hand, an increasing number of functions—and therefore components —are to be included in each piece of terminal equipment, in particular in the field of consumer electronics, while the terminal equipment itself is becoming ever smaller. Consequently, ever less room is available on the application circuit boards for the individual components.
With micromechanical inertial sensors of the type in question here, the accelerations are detected with the aid of the micromechanical sensor structure of the MEMS element and evaluated with the aid of the ASIC element. The micromechanical sensor structure includes at least one elastically suspended seismic mass, which is deflected due to accelerations. These accelerations may also be induced by centrifugal forces or rotary movements. With the aid of suitable circuitry means, the deflections of the seismic mass are converted into electric signals, which are then sent to the evaluation circuit on the ASIC element. The larger the seismic mass, the greater is also its deflection and thus also the greater is the measuring sensitivity of the sensor.
A method for manufacturing a micromechanical inertial sensor of the type defined at the outset is described in US Patent Application Publication No. 2010/0109102 A1. The known method is directed to a processed ASIC substrate having the circuit functions of the inertial sensor component to be manufactured. An insulating layer is deposited on the processed front side of the ASIC substrate and structured. The supports of a standoff structure for the mounting of an MEMS substrate are created. The unstructured MEMS substrate is bonded to the standoff structure and then thinned down to a predefined structural height. Only then is the MEMS substrate structured. In a first structuring step, through-openings are created in the MEMS substrate, which also extend through the supports of the standoff structure down to the ASIC substrate. These through-openings are then filled with an electrically conductive material and thus form through-contacts to the ASIC substrate. Only then in a second structuring step is the micromechanical sensor structure having the seismic mass, which extends over the entire thickness of the MEMS substrate, exposed. A prestructured cap wafer is then mounted above the micromechanical sensor structure, so that it is hermetically enclosed between the ASIC substrate and the cap wafer. Only then are the components released from the wafer composite and separated.
The known method permits an inexpensive mass production of robust components having a micromechanical sensor function and a signal processing circuit since not only are the individual component parts manufactured here in the wafer composite—i.e., the ASIC element, the MEMS element and the cap—but also their assembly to form one component is implemented on the wafer level. The MEMS functions and the ASIC functions may be tested at the wafer level and even the calibration of the individual components may still be carried out on the wafer level before they are separated. Furthermore, the known components require a comparatively small mounting area due to the stacked design, which has positive effects on the manufacturing costs of the terminal equipment.